# Questions tagged [meteorology]

The study of how the earth's atmosphere works, including weather forecasting. Use this tag for questions about the earth's weather. When asking questions specifically about the atmosphere, also include the [atmosphere] tag.

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### Madden-Julian Oscillation (MJO) - How to interpret the index?

How the Madden-Julian Oscillation (MJO) index can be interpret? Let's suppose I have got an MJO index value of 0.6 in a given day, what this does mean? Does 0.6 represents a weak MJO? Data from ...
3k views

### Extracting Regional Data from ERA5

This is coming from a newcomer, so please be kind. As I delve into the world of meteo data and reanalysis for the first time, I found that acquiring weather data is a lengthy process, so I'm shouting ...
4k views

### How to calculate relative humidity from temperature, dew point, and pressure?

Is there a formula given the temperature, dew point, and pressure to find relative humidity? I have seen several calculators like this one, but I would like to know how to calculate this myself. I ...
71 views

### Roughly what proportion of a cloud does 'rain out'?

What proportion of the water in a cloud will 'rain out'? Or, comparing the cloud before and after it has rained, what proportion of the water is left afterwards? I really have no idea so am just ...
3k views

### What are the farthest Time Zone locations? [closed]

What place in the world has the farthest time zone? I heard it was Kiribati but then I found that Apia (Samoa) is further. So, is there anyplace that is the farthest in time than these two? What about ...
253 views

### Temperature Advection using finite differences with gridded data

Advection of a scalar quantity, such as temperature (T), by the horizontal wind, is defined as follows: $-\textbf{U}\cdot\nabla T$ where $\textbf{U}$ is the horizontal wind vector, $\textbf{U}=(u,v)$...
79 views

### Data for plotting tephigrams

I want to plot some tephigrams. Where can I find pressure, temperature and dewpoint data in text format?
47 views

### Any appreciable differences in microclimate on the shores of small mountain streams?

I have land in India (the tropics), in the hills, on a slope from 6800 feet - 5200 ft altitude (roughly). At that lowest point there's a stream of about 10-15m across. On one side is our land, on the ...
177 views

### What are these Gizmos at Mauna Loa Observatory?

Artist Rosten Wu's Vimeo channel has a video title Bridging Time and there is discussion about the Keeling Curve and the site where it all began in Hawaii. In the video there is a shot of a weather ...
449 views

### How do I interpret this “sky cover” chart?

The image below is a screenshot of forecasted sky cover in percentage for various parts of Arizona. Is the sky cover percentage the percentage of each pixel that has cloud, or is it the percentage of ...
44 views

### Topography and flash flooding

I'm looking for a study or document showing the effect of the topography, slopes, the sea level and the tide on flash flooding occurrence. Thanks in advance
79 views

### What do the little flags on these martian wind speed data points mean?

According to this answer the weather at the InSight lander on Mars can now be seen online at https://mars.nasa.gov/insight/weather/ This includes the wind speed and I believe the direction (if that's ...
172 views

### Rainbow dynamics?

How would steam refract light compared to fog and how would the rainbow appear? Does the temperature of the water drop or ice crystal effect the rainbow in any way? I know the size of the water drop ...
132 views

### Why is convective precipitation associated with heavy rains?

Why is convective precipitation associated with heavy rains? As per wikipedia's page on Atmospheric Convection: "Moist convection leads to thunderstorm development, which is often responsible for ...
38 views

### Where can I find a list of snow fall recording stations in my zip code?

Where can I find the locations on snow fall recording stations in a particular United States county or zip code? Is there a way that I can find an hour by hour recent history of snow fall? Hour by ...
67 views

### Figuring out the temperature at the tropopause

Either I am misunderstanding something, or reading conflicting information. Likely the former. First off, the tropopause is defined as the boundary between the troposphere and the stratosphere. That ...
160 views

### How much further can weather forecasting models go before the limits of Chaos Theory set in?

Refer to a report here that mentions the huge advancement in weather forecasting models since the 1980s: How much better? āA modern five-day forecast is as accurate as a one-day forecast was in ...
149 views

### Did temperature for the US state of Illinois reach an all-time record low 1/31/2019?

The State Climatologist Office for Illinois says the all time low temperature of Illinois was -36 Ā°F, with a report of -37 Ā°F in 2009 being disqualified. This morning, the station Sinnissippi ...
5k views

### Does the US National Weather Service use Celsius or Fahrenheit?

This tweet from the National Weather Service in LaCrosse, Wisconsin, USA says: We have officially hit -30 here at the NWS La Crosse office as of 520 a.m. The wind chill is -54. Be sure to dress ...
154 views

### How to plot orography for vertical profile of a certain variable along pressure levels in GRADS

I am using GRADS (1, 2, 3) to plot ERA reanalysis relative humidity profile for latitudinal average of 15N to 37N, and along the longitude from 40E to 130E. The orography is quite obvious and thus ...
355 views

### Unstable North Polar Vortex?

What would cause a polar vortex to become unstable a split into 3 smaller ones? How rare is this and what long term effects could this cause if the vortex stays unstable? http://www.severe-weather.eu/...
153 views

### Where can I find information about monthly seasonal change in a given area?

I have searched Google for almost an hour with no result. I'm looking for something like, "Indonesia, January to August is rain season, September to December is hot season". I can't use the old ...
129 views

### Is pollution a contributing factor to freezing rain?

I have been to different places with nearly the same freezing temperatures, around -2Ā°C, but only at some specific places I repetitively experienced freezing rain. One common factor at these places ...
227 views

### Were there any polar vortexes in 2018?

Were there any polar vortexes in 2018? On what dates? I want to see what the weather looked like on those dates: https://www.youtube.com/watch?v=FPuDPxK88g0 Yes I know. You would think that I could ...
54 views

### What causes frozen “shooting water” spikes from ice covered water in the winter?

I have seen things like this appear once or twice on cold winter mornings, a frozen spike of water from an ice-covered container or very small body of water (puddle). I found the photo below at Mel ...
84 views

### Does wind chill work in deserts?

Wind chill works by removing the layer of heated air around your body. However in a hot area, say a desert, wouldn't the air around be hotter than your body or at least much closer to it than cold air?...
7k views

### Continuous lightning for over an hour; is this phenomenon common and does it have a name?

A few months ago, I witnessed something off the coast of Florida that I have never seen in my life. From my apartment, from about 10PM - 12AM, I saw pretty much continuous cloud to cloud lightning. I ...
207 views

### Circular rain cloud observed in rain radar

This circular rain pattern was observed in Sydneyās rain radar today. It remained for the entire loop, wiggling around a bit but mostly staying in the same place. The fact that itās centred around ...
100 views

### How can I convert a CERA-20C total precipitation dataset of "monthly means of daily means' (edmo) to mm/month?

I downloaded an edmo dataset of 1 ensemble of the cera-20c model. I want to convert these data, which are in [m], to mm/month. Further specifications: 0.125/0.125 grid, -29/30/-30/31 area. Example of ...
1k views

### What is this spaceship-shaped cloud?

This tweet from the European Space Agency (ESA)'s Spanish account show a striking photo of a round, flat, "space-ship-shaped" cloud in an otherwise completely clear sky. The stars are out so I assume ...
441 views

### What happens if it rains above the boiling point of water?

The freezing point of water is 32Ā°F. If it rains at a temperature lower than that, it will snow. However, let's say we dig a deep hole not filled with water that goes like 10,000 feet below sea level. ...
27 views

### What is the accepted measure for Wind Coherency (Strength and Direction)

I have wind data from a Met station (Speed and Direction), and I'm looking for a way to characterize a strong coherent wind. AKA - Wind that averages 12 m/s out of the East for 2 days would have a ...
3k views

### How is it possible to use up the water in a region?

The Dead Sea, rivers in California and the Aral Sea are said to be shrinking due to water usage, e.g. for agriculture. Yet the water must go somewhere. After the fields are irrigated, the water ...
475 views

### How to calculate Wind direction from uwind and vwind?

How to calculate wind direction from uwind and vwind? if uwind and vwind are -1.82 , -3.18 respectively
95 views

### how to calculate the average moisture flux over a period of time

I wanna calculate the average moisture flux over a period of time. For example the average moisture flux over an entire summer. I don't have a meteorological background. I have a conceptual confusion ...
74 views

### Is it certain that hundred year floods have finite variance?

It just occurred to me to ask this. It's easy to get a statistical distribution that does not have finite variance. For example, you can sometimes get that when the thing that is measured comes from ...
2k views

### WRF vertical integrated moisture flux using NCL

Does anyone know how to calculate the vertical integrated moisture flux using NCL in WRF. It would be best if you can share a NCL script. Here is my code, I used this code to calculate the averaged ...
206 views

### Are there “transparent” clouds?

Comments below this answer to the question Why are lightning towers at launch pads topped with big hollow tubes with spiral windings and not ālightning rod-shapedā lightning rods? link to a 2013 ...
571 views

### What is are the benefits of map 500 hPa geopotential for weather forecasting?

From the weather forecasting perspective: what is the main reason for showing just map of 500 hPa geopotential? Are there any practical or theoretical reasons? Why do not show 600 hPa geopotential or ...
102 views

### Does snow melt on ice?

I looked up nearly everywhere on the internet, but couldn't find any evidence that snow wouldn't melt because of ice. When I look it up, it instead tells me how salt can melt snow. I'm NOT looking up ...
42 views

### Projecting rectangular stereography centred on 42°N, 10°E

I am reposting from GIS Stack Exchange as here might also be someone who might help: I have a precipitation GRIB2 file obtained at EUMETSAT H-SAF I am able to decode it to ascii but the software I am ...
88 views

### Are global temperatures, specifically between the two hemispheres, in balance?

I've anecdotally but repeatedly observed a certain balance between temperatures in the two hemispheres. For example, early this year (2018), while Europe was under a late winter spell, weather here in ...
143 views

### Difference between GDAS and GFS data

What is the exact difference between GFS 0.25 and GDAS 0.25 data which is available in http://nomads.ncep.noaa.gov/. And are the GFS 0.5 and 1 degree data available in the above url and here the same?...
42 views

### Why do tethered aerostats have lower persistence than stratospheric balloons?

We have been thinking of using Aerostats/Balloons for an environmental monitoring project in our university. We have been considering 2 options: Tethered Aerostats (which fly upto 1 km) and ...
168 views

### Judging wind speed based on flags and inland-water observations

About a year ago, I took this video along the Hudson river in NY, and I'm trying to figure out the Beaufort number based on the water and the flags. https://www.youtube.com/watch?v=nqjvTALRWW8 The ...
31 views

### How to create Indonesian environmental conditions in India?

Need to create and maintain Biofloc for fish farming in India, it's really successful in Indonesia and I believe it's due to environmental conditions. Can we replicate the same in India?
120 views

### What's the default meaning of “Valid” in NOAA weather map?

NOAA weather forecast maps often include a valid time period, e.g: "valid from time1 thru time2." However, many maps only indicate a single time, e.g: "valid time1." In the absence of other ...
126 views

### Why don't tropical cyclones hit Hawaii?

Image by Wikipedia user Citynoise using NOAA data. If you look at this map of tropical cyclone tracks, you'll notice that there's a gap in the central northern Pacific where tropical cyclones ...
419 views

### If storms form above low pressure regions, why doesn't the eye of a hurricane, a low pressure region, have any storms?

If this is due to the Coriolis Effect, my other question would be how does the wind go upwards to form the storm clouds?